<html>                                                                  
 <head>                                                                  
 <script type="text/javascript" src="jquery.js"></script>          
 <script type="text/javascript">                                         
   // we will add our javascript code here   
   
   
   $(document).ready(function() {
   $("a").click(function() {
     alert("Hello world!");
   });
 });                                  
 </script>                                                               
 </head>                                                                 
 <body>                                                                  
   <!-- we will add our HTML content here --> 
   
    <a href="">Link</a>                                       
 </body>                                                                 
 </html>